It is unfortunate that the book didn't come with a hard cover, but I of course knew that when i bought it.Other than this the book is written nicely with a lot nice examples and exercises.Furthermore will you find all the more difficult proves inside the book, which is nice.

This puzzle has 3 difficulty levels.The first level everyone can solve, so everyone would like this puzzle.The second level is a bit more challenging.The third level is the fun one for me, with really challenging puzzles to solve.